The invention relates to diffusion ovens and to a process for the treatment of semiconductor wafers.
It is known in the art to subject materials such as semiconductor wafers to various treatment processes, such as doping, in quartz pipes. Semiconductor wafers can be doped at high temperatures through contct with an atmosphere containing dopant materials. However, problems exist with this method due to the fact that such treatment must be undertaken with complete avoidance of contamination. In this process, semiconductor wafers must be put into the quartz pipes mechanically, and the semiconductor wafers are always subject to an insufficiently pure atmosphere. In known processes, the semiconductor wafers are put into a hot quartz pipe, which is sealed, and into which the treatment atmosphere is introduced. The preliminary treatment thus ensures in a mixture of laboratory atmosphere and treatment gas, and the semiconductor wafers are subjected to high temperatures from the beginning.
To alleviate disadvantages resulting therefrom, it has been suggested to place a prechamber in front of the quartz pipe (main treatment chamber), and the semiconductor wafers would move through the prechamber to the quartz pipe via a passageway provided with seals. In this system, the problem of mixing atmospheres is somewhat alleviated. However, a new problem results due to the fact that the temperature distribution in the quartz pipe is very nonuniform due to heat radiation coming through the opening of the quartz pipe into the prechamber. This problem is directly related to the inside diameter dimension of the quartz pipe or, correspondingly, to the diameter of the semiconductor wafer to be treated.